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  • The most basic function of bodily fat is self-storage of food reserves.

  • In prehistoric times, natural selection favored genotypes

  • that could endure harsh conditions by stocking the most fat.

  • With chronic malnutrition being the norm for most of human history,

  • genetics evolved to favor fat storage.

  • So when did body fat become problematic?

  • The negative impacts of being overweight were not even noted in medical literature

  • until as late as the 18th century.

  • Then, technological advances coupled with public health measures

  • resulted in the betterment of the quantity, quality, and variety of food.

  • Sustained abundance of good food enabled a healthier population

  • to boom economically.

  • Output increased, and with it, leisure time

  • and waistlines.

  • By the mid 19th century, being excessively overweight, or obese,

  • was recognized as a cause of ill health,

  • and another century later, declared deadly.

  • What is the distinction between being overweight and being obese?

  • A calculation called the BMI breaks it down for us.

  • For example, if someone weighs 65 kilgorams

  • and is 1.5 meters tall,

  • they have a BMI of about 29.

  • Obesity is a condition of excess body fat

  • that occurs when a person's BMI is above 30,

  • just over the overweight range of 25 to 29.9.

  • While BMI can be a helpful estimate of healthy weight,

  • actual body fat percentage can only really be determined

  • by also considering information like waist circumference

  • and muscle mass.

  • Athletes, for instance, have a naturally higher BMI.

  • So how does a person become obese?

  • At its most basic, obesity is caused by energy imbalance.

  • If the energy input from calories

  • is greater than the energy output from physical activity,

  • the body stores the extra calories as fat.

  • In most cases, this imbalance comes from a combination of circumstances

  • and choices.

  • Adults should be getting at least 2.5 hours of exercise each week,

  • and children a whole hour per day.

  • But globally, one in four adults and eight out of ten adolescents

  • aren't active enough.

  • Calorie-dense processed foods and growing portion sizes

  • coupled with pervasive marketing

  • lead to passive overeating.

  • And scarce resources,

  • and a lack of access to healthy, affordable foods

  • creates an even greater risk in disadvantaged communities.

  • Yet, our genetic makeup also plays a part.

  • Studies on families and on separated twins

  • have shown a clear causal hereditary relationship to weight gain.

  • Recent studies have also found a link between obesity

  • and variations in the bacteria species that live in our digestive systems.

  • No matter the cause, obesity is an escalating global epidemic.

  • It substantially raises the probability of diseases,

  • like diabetes,

  • heart disease,

  • stroke,

  • high blood pressure,

  • and cancer.

  • It affects virtually all ages, genders, and socioeconomic groups

  • in both developed and developing countries.

  • With a 60% rise in child obesity globally over just two decades,

  • the problem is too significant to ignore.

  • Once a person is obese, the climb to recovery becomes progressively steeper.

  • Hormonal and metabolic changes reduce the body's response to overeating.

  • After losing weight, a formerly overweight person burns less calories

  • doing the same exercises

  • as a person who is naturally the same weight,

  • making it much more difficult to shed the excess fat.

  • And as people gain weight,

  • damaged to signaling pathways makes it increasingly difficult

  • for the brain to measure food intake and fat storage.

  • There is, however, some evidence

  • that well-monitored, long-term changes in behavior

  • can lead to improvements in obesity-related health issues.

  • And weight loss from sustained lifestyle changes,

  • or invasive treatments like bariatric surgery,

  • can improve insulin resistance and decrease inflammation.

  • What was once an advantage for survival is now working against us.

  • As the world's population continues to slow down and get bigger,

  • moving and consciously eating our way towards a healthier weight

  • is essential to our overall well-being.

  • And with the epidemic affecting every country in the world

  • for different socioeconomic reasons,

  • obesity cannot be seen as an isolated issue.

  • More global measures for prevention

  • are essential to manage the weight of the world.

The most basic function of bodily fat is self-storage of food reserves.

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B2 US TED-Ed obesity fat bmi overweight weight

【TED-Ed】What is obesity? - Mia Nacamulli

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    Sh, Gang (Aaron) posted on 2016/07/05
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